It is known that an electronic device encapsulated by plastic on a lead frame has flash which is formed on the lead parts when the device is encapsulated during the molding process. To remove this flash, the lead frame is typically cleaned by either dry or wet blasting processes, with the blasting media (whether wet or dry) typically involving some type of abrasive particle.
An example of a deburring and cleaning apparatus for plastic-packaged electronic devices is disclosed in Japanese provisional patent Publication SHO-60-36155. This apparatus involves a first pair of belt conveyors which clamp in cantilever style one side of the lead frame as it extends in a lengthwise direction so that a first blasting nozzle can blast the non-clamped side of the lead frame, and a second pair of conveyor belts also clamp in cantilever style the other side of the lead frame so that a second nozzle can blast the other side of the lead frame.
Another example of a deburring and cleaning apparatus for an electronic device encapsulated by plastics, such as a lead frame arrangement, is disclosed in Japanese patent Publication SHO-59-10578. This latter apparatus has a pair of endless belts having reaches running in parallel and having clamping devices thereon for holding the sides of a lead frame therebetween so that the lead frame is transported through a blasting chamber having blasting and washing nozzles therein for treating the lead frame.
While the apparatus disclosed in the publications mentioned above have been utilized to effect burr removal and cleaning of plastic-encapsulated electronic devices, nevertheless it has been observed that such apparatus experience undesirable failures and operational limitations. For example, failures due to jamming or falling of the lead frame (i.e. workpiece) have been observed. Further, portions of the lead frame where no deburring is necessary are also blasted and, due to the fact that the conveyor arrangements generally only loosely hold the workpiece, this can cause undesired roughening and marring of the workpiece package. Further, with apparatus of the aforementioned type, particularly those using belt conveyor systems, the overall apparatus requires substantial length and width which, when coupled with all of the required treatment steps such as washing, rinsing, air blowing and drying, results in a linear arrangement which occupies an undesirably large space.
Accordingly, the present invention relates to a deburring and cleaning apparatus which is believed to represent a significant improvement over prior apparatuses used for this purpose, such as apparatuses of the type described above. In particular, the improved apparatus permits the complete deburring and cleaning process to be carried out utilizing minimal floor space in the processing plant. Further, the entire cleaning process including the deflashing or deburring, washing, rinsing, airblowing and drying of the plastic-packaged electronic device can be easily automated and carried out as a continuous cycle. The overall operational efficiency and cleaning rate achieved by the process carried out in this improved apparatus thus represents a significant improvement over the prior structures.
In the apparatus of the present invention, there is provided a main housing chamber having a drum supported therein for incremental step-like rotation about a substantially horizontal axis. The drum has a plurality of axially extending walls which are spaced circumferentially therearound and project radially outwardly so as to define a plurality of radially-opening compartments. The drum also mounts a releasable holding device within each of the compartments adapted for holding a workpiece, such as a lead frame assembly. A slide assembly is linearly reciprocally mounted on the housing for cyclic movement generally parallel with the horizontal rotational axis, and mounts thereon a plurality of nozzle assemblies which are aligned with individual compartments in the drum so as to linearly reciprocate lengthwise of a respective compartment. With the drum in a first rotational position, one of the compartments is aligned with a first station which permits a finished workpiece to be removed from the holder and a further workpiece to be positioned therein. The drum is thereafter rotatably stepped to a second station wherein the previously loaded workpiece is subject to blasting with an abrasive slurry due to linear reciprocation of a slurry-blasting nozzle longitudinally of the compartment. During subsequent incremental steps to succeeding work stations, the workpiece is again subjected to subsequent treating steps such as washing, rinsing and drying due to respective nozzle arrangements being linearly reciprocated lengthwise of the respective compartment. Following completion of the required steps, the compartment returns to the original loading station whereupon the finished workpiece is removed. In this manner, the complete finishing (that is, the deburring and cleaning) of the workpiece is accomplished due to a series of rotatable incremental steps as the drum undergoes one revolution.
In the improved apparatus of the present invention, as briefly described above, there is provided a driving actuating mechanism which is disposed externally of the drum and which is designed to operate with a driven actuator arrangement mounted on the drum, one such driven actuator arrangement being associated with each compartment of the drum for controlling the respective workpiece holder mechanism. The driving actuating mechanism cooperates with the driven actuator mechanism which is disposed in the loading and unloading station.
In the improved arrangement of the present invention, as described above, there is also preferably provided an improved nozzle arrangement associated with the compartment in which the abrasive slurry is blasted against the workpiece. This nozzle arrangement involves an opposed pair of nozzles which are directed generally toward one another for simultaneously blasting opposite sides of the workpiece, and each of these nozzles has a generally elongated nozzle opening which extends transverse to the linear direction of reciprocation so as to discharge a wide band of abrasive slurry which can effectively abrasively clean the entire width of the workpiece during both the forward and rearward traverse of the nozzle arrangement.
Other objects and purposes of the improved apparatus of the present invention will be apparent upon reading the following specification and inspecting the accompanying drawings.